Recent developments in catalytic asymmetric aldol reactions have been summarized. Enantioselective aldol reactions are important methods to synthesize β-hydroxy carbonyl compounds in optical pure form, and as such, numerous successful chiral catalysts were designed and applied for asymmetric aldol reactions. This review article is organized under the categories of: (1) catalytic enantioselective aldol reactions of preformed enolates, (2) catalytic enantioselective direct-type aldol reactions using chiral metal catalysts, (3) catalytic enantioselective direct-type aldol reactions using organocatalysts, (4) catalytic enantioselective aldol reactions in aqueous media. Examples of the aldol reactions that employ simple carbonyl compounds will be also the focus of this review.
We have discovered a new class of cooperative catalytic system, consisting of heterogeneous polymer-immobilized bimetallic Pt/Ir alloyed nanoclusters (NCs) and 4-tert-butylcatechol, for the aerobic oxidation of amines to imines under ambient conditions. After optimization, the desired imines were obtained in good to excellent yields with broad substrate scope. The reaction rate was determined to be first-order with respect to the substrate and catechol and zero-order for the alloyed Pt/Ir NC catalyst. Control studies revealed that both the heterogeneous NC catalyst and 4-tert-butylcatechol are essential and act cooperatively to facilitate the aerobic oxidation under mild conditions.
The copper(II)-catalyzed aerobic oxidative coupling reaction between aryl boronic acids and aniline derivatives was found to be improved significantly under visible-light-mediated photoredox catalysis. The substrate scope of this oxidative Chan-Lam reaction was thus expanded to include electron-deficient aryl boronic acids as viable starting materials.
A simple and efficient synthesis of oxaz-A C H T U N G T R E N N U N G olidinones was developed through a copper-catalyzed coupling of aldehydes, amines, and terminal alkynes under atmospheric pressure of carbon dioxide.
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